Effect of phonophoresis with dexamethasone on adrenal function

One of the side effects of corticosteroid ingestion and inhalants is suppression of the adrenal glands. Phonophoresis of topically applied corticosteroids is commonly used to treat musculoskeletal inflammatory conditions. The purpose of this study was to determine whether phonophoresis with dexamethasone sodium phosphate affected adrenal function. The subjects included 28 male volunteers (mean = 25.3 years, SD = 6.4) who received phonophoresis to the left shoulder every other day for 2 weeks. Subjects were randomly assigned to one of four groups, including a control group (N = 8), an ultrasound group (N = 8), a .33% dexamethasone group (N = 7), and a ultrasound with .33% dexamethasone group (N = 5). Adrenal function was assessed by 24-hour urinary-free cortisol (microgram cortisol/g creatinine) collected two days prior to and following the phonophoresis treatments. A nonparametric analysis of variance using a split plot factorial design was calculated for ranked urinary-free cortisol scores and found no significant (p > 0.05) differences in urinary-free cortisol levels between the four groups and between the four collection days, and there were no significant (p > 0.05) interactions exhibited between group and collection day. This study suggests that phonophoresis with dexamethasone sodium phosphate, using common clinical parameters, does not cause dexamethasone sodium phosphate to become systemic in large enough quantities to impair adrenal function.